How project complexity undermines benefit realisation

A complicated project has many elements, but their relationships are knowable and solvable with enough effort and expertise.

A complex project has elements whose relationships are unpredictable and shift as the project evolves. Complexity isn't about difficulty; it's about how interdependent elements like tasks, stakeholders, technology and external forces interact in ways that can't be fully planned for upfront. That's why complexity requires "sensing, experimentation and adjustment" rather than a fixed plan.

This matters for benefits specifically because benefits realisation is a long-horizon outcome. A task can be completed correctly and on schedule while the underlying assumptions about why it creates value quietly become obsolete.

Why complexity erodes benefits rather than just derailing execution

The PMI's Pulse of the Profession 2026 report's headline finding is that 31% of complex projects fail to achieve the full scope of their originally intended benefits — more than twice the rate for projects overall. The mechanism behind that number is what's interesting: complexity produces three clustering effects, and the most common one is precisely benefits-related:

• Value/Alignment Gaps (61% of complex projects experience this) are the most pervasive consequence. These are projects that deliver outputs while losing sight of outcomes. The project crosses the finish line technically intact but no longer serves the purpose it was meant to. This happens because complexity causes scope and requirements to shift, not from indecision, but because "the world around the project is changing faster than the original plan."

• Delivery Disruptions (55%) Missed deadlines and inefficiencies, which are more visible but not necessarily what erodes benefits directly.

• Human Impact (31%) Team fatigue and strain that compounds across projects, degrading the organisation's future capacity to execute.

The key insight is that these three effects often interact rather than occurring in isolation. e.g., a regulatory shift (environmental complexity) triggers new internal approvals (organisational complexity), which increases anxiety and micromanagement (human complexity), which further erodes delivery and alignment.

Why this specifically threatens benefits (not just outputs)

Three mechanisms stand out:

1. Strategic drift. As complexity accumulates unaddressed, the connection between what's being built and why weakens. The project can still "succeed" by conventional output measures (on time, on budget, features delivered) while failing to produce the value it was chartered to create.

2. Reactive scope changes replace deliberate ones. In complex environments, requirements change because external conditions shift, not because of poor planning. Teams using rigid, plan-based approaches treat this as scope creep to resist, rather than a signal to adapt, which can lock in benefit-destroying misalignment.

3. The gap is a systems problem, not a task problem. Teams that treat a project as a list of tasks rather than a web of interdependencies miss the downstream implications of decisions. The PMI report notes that only 23% of project professionals identify systems thinking as critical to navigating complexity, despite academic research finding that the most consequential complexity in projects lies in the interactions among stakeholders, priorities, and shifting expectations.

The mitigating factor

The report's counterpoint is that the mere presence of complexity doesn't determine the outcome, the management of it does. High performers don't face less complexity; they just respond to it differently, through early and ongoing stakeholder alignment, structured frameworks, and treating benefits and outcomes as things to actively protect throughout the project rather than assume as a byproduct of good execution.

Projects where teams were highly effective at managing complexity were rated successful 88% of the time, versus 14% when teams were only slightly effective or ineffective.

That's why complexity, left unmanaged, is such a strong predictor of benefits failure, rather than just delay or overspend.